The present invention relates to a method of mass spectrometry, an apparatus adapted to perform the method and a mass spectrometer. More particularly, but not exclusively, the present invention relates to a method of mass spectrometry comprising the step of associating parent (i.e. precursor) and fragmentation (i.e. daughter) ions from a sample by measuring the parent and fragmentation ions from two or more different areas of the sample and identifying changes in the number of parent ions between the areas in the sample, and corresponding changes in the number of fragmentation ions between the two areas.
It is often desirable to analyse the different areas of a biological sample to identify the substituents of the sample in the different areas. In order to perform this method, a user may perform an imaging mass spectrometry method. In such a method, the user can irradiate spots within the sample to produce ions, which reflect the constituents of the sample at the spatial position where the irradiation occurred.
Often, particularly where lipids are present in the sample, it can be difficult to identify what many of the constituents within the sample may be. In order to determine the constituents, further information relating to the structure of the constituents may be desirable. It may therefore be desirable to perform an MS/MS experiment, to give further structural information relating to the sample.
It is known to perform MS/MS on selected parent ions, and to investigate the fragments that are associated with those parents in order to identify the species that is produced. However, this approach requires parent ion selection, and results in limited information being available during the analysis, and limiting the number of components that can be identified.
Similarly, it is known to acquire a full parent ion spectrum, and a fragment ion spectrum without any mass selection. However, in this instance, it is not possible to identify which fragments result from which parent ions, meaning that identification of components within the sample is extremely difficult.
The present invention seeks to overcome the problems of the prior art.